System and method for image processing

ABSTRACT

Mechanisms for image processing are provided. A computing device comprises a memory, an input device, a display, and a processor. The processor is configured to: acquire a three-dimensional image of an anatomical structure and store it in the memory. The processor renders on the display (i) an initial volume of the three-dimensional image corresponding to an initial portion of the anatomical structure, and (ii) a moveable control element. The initial volume has an outer surface defined by a position of the control element. The processor receives input data updating the position of the control element relative to the initial volume; and renders on the display, in place of the initial volume, a further volume of the three-dimensional image, corresponding to a further portion of the anatomical structure and having a further outer surface defined by the updated position of the control element.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation of U.S. application Ser. No.15/510,175, filed Sep. 15, 2014, the contents of which is incorporatedherein by reference.

FIELD

The specification relates generally to medical imaging, and specificallyto a computing device, system and method for image processing.

BACKGROUND

The planning and execution of surgical procedures, particularly complexprocedures such as brain surgery, may require the gathering andorganization of large volumes of information, including various medicalimages of the patient. Such images can include, for example, MRI scans.

Accessing such information, particularly during a surgical procedure,may require extensive preparation of different image views prior to theprocedure; in other cases, significant portions of the images may simplynot be available during the procedure, or may require additionaloperators and time-consuming programming and computational efforts toproduce.

SUMMARY

According to an aspect of the specification, a computing device isprovided, comprising: a memory; an input device; a display; and aprocessor interconnected with the memory, the input device and thedisplay, the processor configured to: acquire a three-dimensional imageof an anatomical structure of a patient and store the three-dimensionalimage in the memory; render on the display (i) an initial volume of thethree-dimensional image corresponding to an initial portion of theanatomical structure, and (ii) a moveable control element; the initialvolume having an initial outer surface defined by a position of thecontrol element; receive, from the input device, input data updating theposition of the control element on the display relative to the initialvolume; responsive to receiving the input data, render on the display,in place of the initial volume, a further volume of thethree-dimensional image, corresponding to a further portion of theanatomical structure and having a further outer surface defined by theupdated position of the control element; the processor configured toselect the further volume by identifying a portion of thethree-dimensional images that intersects with the at least one plane orvolume, and excluding the identified portion from the further volume.

According to another aspect of the specification, method is provided ofprocessing images in a computing device having a memory, an inputdevice, a display and a processor interconnected with the memory, theinput device and the display, the method comprising: acquiring athree-dimensional image of an anatomical structure of a patient andstoring the three-dimensional image in the memory; at the processor,rendering on the display (i) an initial volume of the three-dimensionalimage corresponding to an initial portion of the anatomical structure,and (ii) a moveable control element; the initial volume having aninitial outer surface defined by a position of the control element;receiving, at the processor from the input device, input data updatingthe position of the control element on the display relative to theinitial volume; responsive to receiving the input data, controlling thedisplay at the processor to render, in place of the initial volume, afurther volume of the three-dimensional image, corresponding to afurther portion of the anatomical structure and having a further outersurface defined by the updated position of the control element.

BRIEF DESCRIPTIONS OF THE DRAWINGS

Embodiments are described with reference to the following figures, inwhich:

FIG. 1 depicts an operating theatre, according to a non-limitingembodiment;

FIG. 2 depicts a computing device for deployment in the operatingtheatre of FIG. 1, according to a non-limiting embodiment;

FIG. 3 depicts a method of processing images, according to anon-limiting embodiment;

FIG. 4 depicts a method of rendering initial and further volumes in themethod of FIG. 3, according to a non-limiting embodiment;

FIG. 5 depicts an example of the performance of block 310 of the methodof FIG. 3, according to a non-limiting embodiment;

FIG. 6 depicts another example of the performance of block 310 of themethod of FIG. 3, according to a non-limiting embodiment;

FIG. 7 depicts a further example of the performance of block 310 of themethod of FIG. 3, according to a non-limiting embodiment;

FIGS. 8A and 8B depict examples of performances of block 320, accordingto a non-limiting embodiment;

FIGS. 9A and 9B depict other examples of performances of block 320,according to a non-limiting embodiment; and

FIGS. 10A and 10B depict further examples of performances of block 320,according to a non-limiting embodiment.

DETAILED DESCRIPTION OF THE EMBODIMENTS

Various embodiments and aspects of the disclosure will be described withreference to details discussed below. The following description anddrawings are illustrative of the disclosure and are not to be construedas limiting the disclosure. Numerous specific details are described toprovide a thorough understanding of various embodiments of the presentdisclosure. However, in certain instances, well-known or conventionaldetails are not described in order to provide a concise discussion ofembodiments of the present disclosure.

As used herein, the terms, “comprises” and “comprising” are to beconstrued as being inclusive and open ended, and not exclusive.Specifically, when used in the specification and claims, the terms,“comprises” and “comprising” and variations thereof mean the specifiedfeatures, steps or components are included. These terms are not to beinterpreted to exclude the presence of other features, steps orcomponents.

Unless defined otherwise, all technical and scientific terms used hereinare intended to have the same meaning as commonly understood to one ofordinary skill in the art.

FIG. 1 depicts a surgical operating theatre 100 in which a healthcareworker 102 (e.g. a surgeon) operates on a patient 104. Specifically,surgeon 102 is shown conducting a minimally invasive surgical procedureon the brain of patient 104. Minimally invasive brain surgery involvesthe insertion and manipulation of instruments into the brain through anopening that is significantly smaller than the portions of skull removedto expose the brain in traditional brain surgery techniques.

The opening through which surgeon 102 inserts and manipulatesinstruments is provided by an access port 106. Access port 106 typicallyincludes a hollow cylindrical device with open ends. During insertion ofaccess port 106 into the brain (after a suitable opening has beendrilled in the skull), an introducer (not shown) is generally insertedinto access port 106. The introducer is typically a cylindrical devicethat slidably engages the internal surface of access port 106 and bearsa conical atraumatic tip to allow for insertion of access port 106 intothe sulcal folds of the brain. Following insertion of access port 106,the introducer may be removed, and access port 106 may then enableinsertion and bimanual manipulation of surgical tools into the brain.Examples of such tools include suctioning devices, scissors, scalpels,cutting devices, imaging devices (e.g. ultrasound sensors) and the like.

Also shown in FIG. 1 is an equipment tower 108 supporting a computingdevice (not shown) such as a desktop computer, as well as one or moredisplays 110 connected to the computing device for displaying imagesprovided by the computing device. The computing device, display 110, orboth, may also be supported by other structures. Indeed, the computingdevice may be located outside of operating theatre 100, and wheremultiple displays are provided, at least one display may also be locatedoutside of operating theatre 100.

Equipment tower 108 may also support a tracking system 112. Trackingsystem 112, when included, is generally configured to track thepositions of one or more reflective markers (not shown) mounted onaccess port 102, any of the above-mentioned surgical tools, or anycombination thereof. Such markers, also referred to as fiducial markers,may also be mounted on patient 104, for example at various points onpatient 104's head. Tracking system 112 may therefore include a camera(e.g. a stereo camera) and a computing device (either the same device asmentioned above or a separate device) configured to locate the fiducialmarkers in the images captured by the camera, and determine the spatialpositions of those markers within the operating theatre. The spatialpositions may be provided by tracking system 112 to the computing devicein equipment tower 108 for subsequent use. An example of tracking system112 is the “Polaris” system available from Northern Digital Inc.

Also shown in FIG. 1 is an automated articulated arm 114, also referredto as a robotic arm, carrying an external scope 116 (i.e. external topatient 104). External scope 116 may be positioned over access port 102by robotic arm 114, and may capture images of the brain of patient 104for presentation on display 110. The movement of robotic arm 114 toplace external scope 116 correctly over access port 102 may be guided bytracking system 112 and the computing device in equipment tower 108. Theimages from external scope 116 presented on display 110 may be overlaidwith other images, including images obtained prior to the surgicalprocedure. The images presented on display 110 may also display virtualmodels of surgical instruments present in the field of view of trackingsystem 112 (the positions and orientations of the models having beendetermined by tracking system 112 from the positions of the markersmentioned above).

Both before and during a surgical procedure such as the one illustratedin FIG. 1, images of anatomical structures within patient 104 may beobtained using various imaging modalities. For example, images of thebrain of patient 104 may be obtained using Magnetic Resonance Imaging(MRI), Optical Coherence Tomography (OCT), ultrasound, ComputedTomography (CT), optical spectroscopy and the like. As will be discussedin further detail below, such images may be stored in the computingdevice mentioned above, and subsequently processed by the computingdevice for presentation and manipulation on display 110.

Before a discussion of the functionality of the computing device, abrief description of the components of the computing device will beprovided. Referring to FIG. 2, a computing device 200 is depicted,including a central processing unit (also referred to as amicroprocessor or simply a processor) 202 interconnected with anon-transitory computer readable storage medium such as a memory 204.

Processor 202 and memory 204 are generally comprised of one or moreintegrated circuits (ICs), and can have a variety of structures, as willnow occur to those skilled in the art (for example, more than one CPUcan be provided). Memory 204 can be any suitable combination of volatile(e.g. Random Access Memory (“RAM”)) and non-volatile (e.g. read onlymemory (“ROM”), Electrically Erasable Programmable Read Only Memory(“EEPROM”), flash memory, magnetic computer storage device, or opticaldisc) memory. In the present example, memory 204 includes both avolatile memory and a non-volatile memory. Other types of non-transitorycomputer readable storage medium are also contemplated, such as compactdiscs (CD-ROM, CD-RW) and digital video discs (DVD).

Computing device 200 can also include a network interface 206interconnected with processor 200. Network interface 206 allowscomputing device 200 to communicate with other computing devices via anetwork (e.g. a local area network (LAN), a wide area network (WAN) orany suitable combination thereof). Network interface 206 thus includesany necessary hardware for communicating over such networks, such asradios, network interface controllers (NICs) and the like.

Computing device 200 can also include an input/output interface 208,including the necessary hardware for interconnecting processor 202 withvarious input and output devices. Interface 208 can include, among othercomponents, a Universal Serial Bus (USB) port, an audio port for sendingand receiving audio data, a Video Graphics Array (VGA), Digital VisualInterface (DVI) or other port for sending and receiving display data,and any other suitable components. In general, I/O interface 208connects computing device 200 to “local” input and output devices, whilenetwork interface 206 connects computing device 200 to “remote”computing devices, which may themselves be connected to additional inputand output devices. This arrangement may be varied, however. Forexample, any suitable combination of the input and output devices to bediscussed below may be connected to computing device 200 via networkinterface 206 rather than I/O interface 208. Indeed, in some embodimentsI/O interface 208 may be omitted entirely, while in other embodimentsnetwork interface 206 may be omitted entirely.

In the present example, via interface 208, computing device 200 can beconnected to input devices including a keyboard and mouse 210, amicrophone 212, as well as scope 116 and tracking system 112, mentionedabove. Also via interface 208, computing device 200 can be connected tooutput devices including illumination or projection components 214 (e.g.lights, projectors and the like), as well as display 110 and robotic arm114 mentioned above. It is contemplated that other combinations ofdevices may also be present, omitting one or more of the above devices,including other input (e.g. touch screens) and output (e.g. speakers,printers) devices, and the like.

Computing device 200 stores, in memory 204, an image manipulationapplication 216 (also referred to herein as application 216) comprisinga plurality of computer readable instructions executable by processor202. When processor 202 executes the instructions of application 216(or, indeed, any other application stored in memory 204), processor 202performs various functions implemented by those instructions, as will bediscussed below. Processor 202, or computing device 200 more generally,is therefore said to be “configured” or “operating” to perform thosefunctions via the execution of application 216.

Also stored in memory 204 is a patient data repository 218. Patient datarepository 218 can contain a surgical plan defining the various steps ofthe minimally invasive surgical procedure to be conducted on patient104, as well as images of patient 104 (e.g. MRI and CT scans).

As mentioned above, computing device 200 is configured, via theexecution of application 216 by processor 202, to perform variousfunctions related to presenting and manipulating images of patient 104on display 110. Those functions will be described in further detailbelow.

Referring now to FIG. 3, a method 300 of processing images is depicted.Method 300 will be discussed in conjunction with its performance oncomputing device 200 as deployed in operating theatre 100. It will beapparent to those skilled in the art, however, that method 300 can alsobe implemented on other computing devices in other systems.

Beginning at block 305, computing device 200 is configured to acquire atleast one three-dimensional image of an anatomical structure of patient104 and store the three-dimensional image in memory 204 (for example, inpatient data repository 218). In the present example, the anatomicalstructure is the brain of patient 104, but a variety of other anatomicalstructures may also be imaged instead of, or in addition to, the brain.The mechanism of acquisition of the image is not particularly limited.For example, computing device 200 can obtain the image directly from animaging device (not shown), such as an MRI scanner. In other examples,computing device 200 can obtain the image from another computing devicewhich itself obtained the image from an imaging device.

The exact nature of the image may also vary. In the present example, thethree-dimensional image is assumed to be an MRI scan. The collection oftwo-dimensional MRI slices, together representing a three-dimensionalscan of the brain, is referred to herein as the three-dimensional image.In other examples other imaging modalities may be employed instead of,or in addition to, MRI.

Proceeding to block 310, computing device 200 is configured to controldisplay 110 (e.g. via I/O interface 208) to render an interface forpresenting and manipulating the three-dimensional image. In general, theinterface includes a rendering of an initial volume of thethree-dimensional image corresponding to an initial portion of theanatomical structure (that is, the brain of patient 104). The interfacerendered at block 310 also includes at least one moveable controlelement, which will be discussed in greater detail below. Broadly, theinitial volume rendered on display 110 has an initial outer surfacedefined by a position of the control element relative to the initialvolume.

In other words, the three-dimensional image contains data depicting agiven volume of the anatomical structure. In the case of the brain, thethree-dimensional image may in fact depict a volume of patient 104 thatis larger than the brain itself. An MRI scan of the brain, for example,can depict the skull as well as the brain. The initial volume renderedon display 110 at block 310 need not contain the entire volume of thethree-dimensional image (although it may contain the entire volume). Theinitial volume referred to above, therefore, is some portion (up to andincluding 100%) of the three-dimensional image. Which portion of thethree-dimensional image is rendered at block 310 is computed byprocessor 204 based on the positions of the above-mentioned controlelements.

As will be discussed in greater detail below, the control elementsdefine geometrical planes or volumes having positions relative to thethree-dimensional image (e.g. coordinates within a coordinate systemassociated with the three-dimensional image). At those positions, theplanes or volumes defined by the control elements intersect with thevolume of the three-dimensional image. Such intersections define theouter surface of the initial volume to be rendered from the completethree-dimensional image. That is, the intersections of the controlelements with the three-dimensional image define the boundaries of theinitial volume to be rendered (i.e. what portion of the image will berendered and what portion will be excluded from the rendering).

Turning now to FIGS. 4-7, three examples of control elements and themanner in which they are rendered and processed by computing device 200will be discussed. FIG. 4 depicts a method 400, performed by computingdevice 200 (via the execution of application 216, discussed earlier), ofperforming blocks 310 and 320 (that is, the rendering steps) of method300. Method 400 will be described with reference to FIGS. 4, 5 and 6,which depicts examples of the interfaces generated at block 310 (and, aswill be seen later herein, at block 320).

Referring to FIG. 4, at block 405, having acquired the three-dimensionalimage, computing device 200 is configured to select one or more controlelements. The definitions of the control elements are stored in memory204, for example as part of application 216. The selection at block 405can be automatic—for example, application 216 can contain instructionsto select a default control element, or set of control elements—or theselection can be received as input data, for example from keyboard/mouse210.

In the present example, three types of control elements arecontemplated, though it will be understood that these are onlyexamples—other types of control elements will occur to those skilled inthe art in light of the present description. As seen in FIG. 4, anycombination of the three types of control elements may be selected. Forsimplicity, the control elements will be discussed individually,however. Thus, when computing device 200 determines that the planecontrol elements have been selected at block 410, performance of method400 proceeds to block 415.

The plane control elements include a plurality of planes. In the presentexample, three orthogonal planes are contemplated, although othernumbers of planes, disposed at other angles relative to each other, mayalso be employed.

The planes each have an initial default location relative to thethree-dimensional image, such that each plane intersects thethree-dimensional image. Thus, it will now be apparent that the planes,by intersecting the three-dimensional image, divide the image intoquadrants (in particular, eight quadrants in the case of threeorthogonal planes). At block 415, computing device 200 is configured toselect one of the quadrants, and clip the intersection of that selectedquadrant and the three-dimensional image, before proceeding to block 310to render the resulting initial volume on display 110.

Referring now to FIG. 5, an example of the interface generated at block310 following the performance of blocks 405, 410 and 415 is illustrated.FIG. 5 depicts an interface 500 generated on display 110 that includes arendering of an initial volume 504 and control elements 508, 512 and 516in the form of orthogonal planes. In the present example, controlelements 508, 512 and 516 are the sagittal, coronal, and transverseanatomical planes, respectively. In addition to initial volume 504,two-dimensional slices of the three-dimensional image are alsoillustrated, each corresponding to the position of one of the threeplanes within the three-dimensional image. The two-dimensional views maybe omitted in other embodiments.

As seen from FIG. 5, initial volume 504 includes the entire volume ofthe three-dimensional image (that is, the MRI scan of patient 104'shead), with the exception of the portion intersected by one of thequadrants defined by planes 508, 512 and 516. The intersecting quadranthas been cut away, or clipped, and therefore is not rendered ininterface 500, which allows certain interior portions of the brain to berendered. In other words, the position of the three planes defines theouter surface of initial volume 504.

Returning to FIG. 4, whether or not the determination at block 410 isaffirmative, at block 420 computing device 200 may also (oralternatively) determine that a cone control element has been selectedat block 405. If the determination at block 420 is affirmative,performance of method 400 proceeds to block 425.

The cone control element is a volume in the shape of a cone, or in someembodiments, a truncated cone, having an initial default positionrelative to the three-dimensional image. At block 425, computing device200 is configured to clip the portion of the three-dimensional imagethat intersects with the conical volume, before proceeding to block 310.

Turning to FIG. 6, an example interface 600 generated as a result of theperformances of blocks 405, 420 and 425 is illustrated. Interface 600includes an initial volume 604 and a control element 608. Controlelement 608 corresponds to a cone 612, which may be omitted frominterface 600 (in the present example, cone 612 is shown in FIG. 6 onlyfor illustrative purposes, and does not appear on interface 600). Moreparticularly, control element 608 comprises an axis 616 along which amodel 620 of an access port may be positioned at various depths relativeto the three-dimensional image (and by extension, to initial volume604). In other words, input data received at processor 204 may act toslide model 620 along axis 616. As seen in FIG. 6, the summit of cone612 coincides with the point of model 620. Thus, as model 620 is movedalong axis 616 towards the brain as represented by the three-dimensionalimage, cone 612 will begin to intersect with the three-dimensionalimage. Computing device 200 is configured to clip any portions of thethree-dimensional image that intersect with cone 612. In the presentexample, however, the default initial position for cone 612 does notintersect with the three-dimensional image, and initial volume 604 hasnot had any portions clipped therefrom by computing device 200.

Returning to FIG. 4, whether or not the determinations at blocks 410 and420 are affirmative, at block 430 computing device 200 may also (oralternatively) determine that a mask control element has been selectedat block 405. If the determination at block 430 is affirmative,performance of method 400 proceeds to block 435.

The mask control element is an irregular surface having an initialdefault position relative to the three-dimensional image. The initialposition of the mask is determined by computing device 200 by anysuitable algorithm or combination of algorithms to identify the borderbetween skull and brain. As mentioned above, images such as MRI scansgenerally include data depicting the entire head of patient 104,including skull and facial features. The mask control element is anestimate of the outer surface of the patient 104's brain, and dividesthe three-dimensional image into an “outer” part representing non-braintissues, and an “inner” part representing brain tissues. At block 435,computing device 200 is configured to clip the portion of thethree-dimensional image that intersects with the above-mentioned outerpart, before proceeding to block 310. Thus, as with the plane and conecontrol elements, the mask control element defines the outer surface ofthe initial volume.

Turning to FIG. 7, an example interface 700 generated as a result of theperformances of blocks 405, 430 and 435 is illustrated. Interface 700includes an initial volume 704 and a control element 708. Controlelement 708 corresponds to the mask, an irregular surface notillustrated in conjunction with initial volume 704. The mask, however,may be illustrated in a second two-dimensional view as an outline 712delineating the boundary between the outer part (excluded from initialvolume 704) and the inner part (included in initial volume 704). Thenature of control element 708 is not particularly limited, and in thepresent example comprises an axis 716 and a depth indicator 720indicating the depth of the mask along axis 716.

As mentioned earlier, the control elements described herein may becombined. For example, while interface 500 does not show the applicationof a mask (thus, the patient 104's skull and ears are visible in initialvolume 504), interface 600 does apply the mask, in addition to cone 612.

Returning now to FIG. 3, having presented an initial interface ondisplay 110, computing device 200 is configured to proceed to block 315.At block 315, processor 204 is configured to receive input data updatingthe position of the control element(s) rendered at block 310, relativeto the initial volume rendered at block 310. In other words, theposition of the control element(s) within the coordinate system of thethree-dimensional image may change in response to input data.

Referring to FIGS. 5, 6 and 7, the input data received at block 315 caninclude the selection and dragging, or other repositioning, or thecontrol elements shown therein. For example, processor 204 may receiveinput data from keyboard/mouse 210 representing a selection and movingoperation performed on any one or more of planes 508, 512 and 516. Withrespect to interface 600, processor 204 may receive input data fromkeyboard/mouse 210 representing a change in depth of model 620 alongaxis 616, a change in angle of axis 616, and the like. With respect tointerface 700, processor 204 may receive input data from keyboard/mouse210 representing a change in depth of depth indicator 720 along axis716. In further embodiments, input data can also be received form atouchscreen interface, a joystick input, a gesture control or a voicecontrol interface.

Having received updated positions for the control elements, computingdevice 200 is configured, at block 320, to control display 110 topresent an updated interface. The updated interface includes a renderingof a further volume of the three-dimensional image, as well as thecontrol elements rendered in block 310, but in their updated positions.The generation of an updated interface is performed as described abovein connection with method 400, substituting the updated control elementpositions for the previous (e.g. initial) control element positions.

Having rendered an updated interface on display 110, computing device200 is configured to repeat blocks 315 and 320 until an exit command isreceived at block 325.

FIGS. 8A and 8B illustrate the interfaces rendered in two subsequentperformances of blocks 315 and 320. FIG. 8A illustrates an interface 800in which the position of plane 516 has been updated to raise plane 516in the superior direction (that is, towards the top of patient 104'shead as depicted by the three-dimensional image). As a result, theclipped quadrant that intersects with the three-dimensional image haschanged in dimensions. In other words, the outer surface of a furthervolume 802 of the three-dimensional image has changed. Although theexample above shows only a translation of plane 516, it is contemplatedthat any of the planes may also be rotated, angled and the like.

FIG. 8B illustrates another interface 804 in which plane 516 has beenreturned to its previous position (as shown in FIG. 5), but in which afurther volume 806 has been rotated on display 110. As mentionedearlier, when the plane control elements are selected at block 405,computing device 200 is configured to select one of the quadrantsdefined by the intersecting planes. In the present example, computingdevice 200 is configured to automatically select the quadrant of whichthe greatest proportion is visible on display 110. Thus, for the sameplane positions, different quadrants may be selected for clipping basedon the position of the illustrated volume on the display.

Turning to FIGS. 9A and 9B, two further interfaces generated atsubsequent performances of blocks 315 and 320 are illustrated, using thecone control element. Interface 900 in FIG. 9A depicts a further volume902 in which control element 608 has been relocated in the inferiordirection (that is, model 620 has been moved down axis 616). As aresult, a portion of the three-dimensional image intersects with cone612, and the intersection portion has been clipped, resulting acone-shaped cavity in further volume 902. Interface 904 in FIG. 9Bdepicts a further volume 906 which has been rotated in comparison tofurther volume 902. In addition, the angle of control element 608 hasbeen altered.

Turning to FIGS. 10A and 10B two further interfaces generated atsubsequent performances of blocks 315 and 320 are illustrated, using themask control element. Interface 1000 in FIG. 10A depicts a furthervolume 1002 of the three-dimensional image, in which depth marker 720has been raised “outwards” from the brain along axis 716, in comparisonwith FIG. 7. Thus, the mask defined by control element 708 defines anouter surface of further volume 1002 that lies outside the outer surfaceof the three-dimensional image for the majority of the patient 104'sskull. Thus, the skull and facial features are visible in further volume1002, as they do not intersect with the “outer” part mentioned earlier.FIG. 10B, in contrast, depicts an interface 1004 in which depth marker720 has been relocated inwardly along axis 716, contracting the mask andthus adjusting the outer surface of a further volume 1006. The boundaryof the mask is clearly visible in FIG. 10B on the two-dimensional pane.

The adjustment of the mask depth as shown in FIGS. 10A and 10B may beimplemented in a variety of ways. In the present example, thebrain/skull boundary detection parameters are not altered. Rather, thoseparameters are set once, and computing device is configured to shifteach point of the mask inwards or outwards by a number of pixels (orvoxels, or any other unit of measurement within the three-dimensionalimage) proportional to the distance travelled by depth marker 720 alongaxis 716.

Variants to the techniques described above are contemplated. Forexample, the three-dimensional image may be supplemented by otherthree-dimensional images acquired by computing device 200. In someembodiments, patient data repository may contain one or more images offluid flow tracts for patient 104, one or more images or models of atumour within the brain of patient 104, and the like. Such images can beoverlaid on the initial and further volumes discussed above. Inaddition, such images can be exempt from the clipping behaviourdiscussed above. Thus, for example, FIG. 10B shows an image 1008 of atumour in conjunction with further volume 1006. As seen in FIG. 10B, thetumour is not subject to the masking behaviour exhibited with furthervolume 1006. It will now be apparent to those skilled in the art thatFIG. 5 also shows an image 524 of a tumour.

As another example, FIG. 9B shows, in addition to further volume 906, animage 908 of fluid tracts. Image 908 can be a portion selected from alarger image of fluid tracts (for example, the selected portion can belimited to those tracts that would be intersected by the access port ifthe access port were inserted to the illustrated position of model 620).

Image overlays such as fluid tracts and tumours may be enabled anddisabled by way of input data received at processor 204 (e.g. fromkeyboard/mouse 210). For example, the interfaces discussed above mayinclude one or more selectable toggle elements for enabling anddisabling such overlays. Other types of overlays contemplated candisplay or hide different types of tissue. For example, thethree-dimensional image can include identifiers of which type of tissueeach voxel (or group of voxels) depicts. Such identifiers may be addedto the three-dimensional image manually, or by execution of a tissueidentification algorithm. An interface 100 on display 110 may theninclude selectable elements that disable or enable the display ofvarious portions of the three-dimensional image. In other words, anadditional selection of data from the three-dimensional image can occurat or before block 310, depending on which tissue types are selected fordisplay. In further variations, certain tissue types may be identifiedas being exempt from the “clipping” behaviour discussed above (similarto the illustration of the tumour model in FIG. 10B, which is exemptfrom the clipping imposed by the mask). Thus, the volumes mentionedabove can correspond to particular tissue types, and computing device200 can render additional volumes whose outer surfaces are not definedby control element positions (as they are exempt from clipping).

In other variations, when an interface includes a two-dimensional view,the corresponding initial or further volume (that is, thethree-dimensional view) may include an illustration of the plane fromwhich the two-dimensional view is taken. This is shown in FIG. 5; asimilar mechanism can be applied to other interfaces, such as that shownin FIGS. 7, 10A and 10B.

In further variations, computing device 200 may colorize controlelements to enhance their visibility on display 110. For example, the“outer” part beyond the boundary of the mask shown in FIGS. 7, 10A and10B may be colorized differently than the inner part. As anotherexample, each one of planes 508, 512 and 516 may be assigned a colour.The planes as illustrated on initial volume 504 and any subsequentlypresented further volumes, as well as in the accompanyingtwo-dimensional views, may bear the same colours.

In other variations, some aspects of the control elements may beconfigurable. For example, the radius of cone 612 may be altered byprocessor 204 in response to input data.

Persons skilled in the art will appreciate that there are yet morealternative implementations and modifications possible for implementingthe embodiments, and that the above implementations and examples areonly illustrations of one or more embodiments. The scope, therefore, isonly to be limited by the claims appended hereto.

We claim:
 1. A computing device comprising: an input device; a display;and a processor configured to: obtain a three-dimensional (3D) image ofa brain and a skull of a patient; detect, based on the three-dimensionalimage, a boundary surface between the brain and the skull; set aninitial position of a clipping mask at the boundary surface; clip the 3Dimage at the clipping mask to select an initial portion of the 3D image;render on the display (i) the initial portion of the 3D image, and (ii)a mask depth control element movable via the input device to adjust theinitial position of the clipping mask; receive an adjusted position ofthe clipping mask via selection of the mask depth control element withthe input device; clip the three-dimensional image at the clipping maskaccording to the adjusted position, to select a further portion of the3D image; and render on the display (i) the further portion of the 3Dimage in place of the initial portion, and (ii) the mask depth controlelement.
 2. The computing device of claim 1, wherein the 3D image is amagnetic resonance imaging (MRI) scan.
 3. The computing device of claim1, wherein the processor is further configured to: obtain an overlayimage depicting an anatomical feature of the brain; and render, on thedisplay, at least a portion of the overlay image simultaneously with oneor more of the initial portion of the 3D image, and the the furtherportion of the 3D image.
 4. The computing device of claim 3, wherein theprocessor is further configured to: render, on the display, a selectabletoggle element for enabling or disabling rendering of the overlay image;and prior to rendering the portion of the overlay image, receive aselection of the toggle element.
 5. The computing device of claim 3,wherein the processor is configured to select the portion of the overlayimage for rendering, independently of the clipping mask.
 6. Thecomputing device of claim 3, wherein the overlay image depicts a set offluid flow tracts in the brain.
 7. The computing device of claim 3,wherein the overlay image depicts a tumor.
 8. A method of processingimages in a computing device having an input device, a display and aprocessor, the method comprising, at the processor: obtaining athree-dimensional (3D) image of a brain and a skull of a patient;detecting, based on the three-dimensional image, a boundary surfacebetween the brain and the skull; setting an initial position of aclipping mask at the boundary surface; clipping the 3D image at theclipping mask to select an initial portion of the 3D image; rendering onthe display (i) the initial portion of the 3D image, and (ii) a maskdepth control element movable via the input device to adjust the initialposition of the clipping mask; receiving an adjusted position of theclipping mask via selection of the mask depth control element with theinput device; clipping the three-dimensional image at the clipping maskaccording to the adjusted position, to select a further portion of the3D image; and rendering on the display (i) the further portion of the 3Dimage in place of the initial portion, and (ii) the mask depth controlelement.
 9. The method of claim 8, wherein the 3D image is a magneticresonance imaging (MRI) scan.
 10. The method of claim 8, furthercomprising: obtaining an overlay image depicting an anatomical featureof the brain; and rendering, on the display, at least a portion of theoverlay image simultaneously with one or more of the initial portion ofthe 3D image, and the the further portion of the 3D image.
 11. Themethod of claim 10, further comprising: rendering, on the display, aselectable toggle element for enabling or disabling rendering of theoverlay image; and prior to rendering the portion of the overlay image,receiving a selection of the toggle element.
 12. The method of claim 10,further comprising: selecting, independently of the clipping mask, theportion of the overlay image for rendering.
 13. The method of claim 10,wherein the overlay image depicts a set of fluid flow tracts in thebrain.
 14. The method of claim 10, wherein the overlay image depicts atumor.